1. Field of the Invention
The present invention relates to a positioning device for a limb extremity more particularly useful in supporting and positioning a foot. The device is particularly intended to set and maintain a foot in an appropriate position to carry-out a radiographic or external measurement procedure, or to take an imprint of the foot or amputation stump. The positioning device is principally characterised in that it allows simultaneous measurement of the top and underside portions of the foot in a xe2x80x9cno-loadxe2x80x9d position, i.e. when the foot is not bearing on a supporting surface.
2. Brief Description of the Prior Art
Several systems have been developed for many years to measure the shape of a foot in order to fabricate a customised footwear article or an orthotic insole to be placed in a shoe or boot for comfort optimisation or therapeutic purpose. The best systems rely on contact-free techniques based on digital cameras, laser or LED scanners and computerised analysis systems to obtain an accurate three-dimensional mapping of the external envelope of the foot. These data are thereafter used to identify or manufacture footwear or orthotic or prosthetic that is best fitted to the foot or stump size and shape. To achieve optimal results or therapeutic objectives, an accurate 3D mapping of the underside of the foot is required in addition to the dimensional information on the upper portion of the foot. Only a few systems of the prior art provide such complete information, still with limited accuracy.
For example, U.S. Pat. No. 4,819,660 (Smithxe2x80x941989) discloses an apparatus comprising a camera head rotated around an amputation stump in a circular path to provide multiple 2D images. The extremity of the stump is supported on a stool. U.S. Pat. No. 5,689,446 (Sundmann et al.xe2x80x941997) an array of gauge pins is used to take the impression of the underside of the foot, while a 3D camera system first acquires the dimensional information of the top of the foot and secondly acquires the image of the conforming gauge pin array once the foot is removed. U.S. Pat. No. 5,457,325 (Hubertyxe2x80x941995) refers to a similar approach to reconstitute the complete outer shape of the foot. In U.S. Pat. No. 5,790,256 (Brown et al.xe2x80x941998), LED arrays scan the sides of the feet while pressure sensitive arrays acquires data on the underside morphology of the feet. U.S. Pat. No. 5,128,880 (Whitexe2x80x941992) teaches a method for measuring the underside of a foot comprising the steps of placing the foot against a reference surface within the scanning field of a scanner, scanning the foot bottom facing surface and displaying the scanned foot image articulating distances of portions of the foot bottom facing surface from the reference surface. However no measurement of the upper portion of the foot is performed in this method. In U.S. Pat. No. 5,164,793 (Wolfersberger et al.xe2x80x941992) a foot is deposed on an inclined plate-glass and 3D information about the top portion is recorded from a laser and camera system, while a camera is taking a 2D image of the underside of the foot to calculate the key length and girth data to fit a shoe. In U.S. Pat. No. 5,671,055 (Whittlesey et al.xe2x80x941997), a three-dimensional profile of the foot of a person standing on a surface is obtained by scanning one side after the other with a laser camera mounted on a turntable. Such a method obviously provides no information about the foot underside but its perimeter. In U.S. Pat. No. 5,804.830 (Shafirxe2x80x941998), radiant-energy emitters and sensors are disposed about a circular ring moving along a foot positioned about the center of said ring. Three-dimensional mapping of the outer contour is obtained but with very low definition of the foot underside since the foot is deposed on supporting plate.
Although the above examples show that adequate contact-free measurement techniques exist to acquire complete dimensional data, no existing system is designed to provide direct contact-free three-dimensional measurement of the upper portion and underside of a foot, with the possibility of performing such measurements simultaneously to avoid distortions due to possible movement of the foot. An integral 3D system could be set-up by combination of certain of the existing techniques with still important limitations, mainly imputable to the foot supporting and positioning device, which introduces interference such as hidden foot areas and modification of the natural foot envelope. Indeed, these systems perform the measurement procedure while the person is standing on a usually transparent surface (fully loaded condition) or with the foot being deposed on an inclined surface in a semi-loaded condition. Hence, the so obtained measurements generally lack information about the underside of the foot and do not take into consideration the best foot behaviour for maximum comfort or therapeutic ends as a function of its global morphology and biomechanics i.e. bone structure, alignment, over or under-pronation, fatty padding etc.
It is a best approach in designing customised footwear and especially orthotics for the treatment of foot or postural deficiencies to base the conception on complete dimensional information acquired in the so-called xe2x80x9cneutral unloaded positionxe2x80x9d of the leg and foot so to implement the appropriate correcting means. U.S. Pat. No. 4,662,079 delivered to Graf et al in 1987 provides a process and apparatus to align a leg and foot in the neutral position to take a physical imprint using plaster or a similar medium. The neutral position can be defined as the most efficient position to accommodate the full range of foot rotation during locomotion. Design of customised footwear and orthotic shall take that information into consideration and not only the dimensioning of the foot in stressed weight-bearing conditions, to allow the foot and body structure to behave with minimal stress and maximal comfort.
Today""s techniques provide faster and more accurate means for gathering foot dimensioning data as aforementioned. It is nevertheless of prime importance, especially in designing athletic or therapeutic footwear, to be able to support the foot in a non-loaded condition and align and maintain it in a natural or neutral position while carrying-out the contact-free measurement. The supporting and positioning device shall therefore be of a type that will not interfere with the dimensional data acquisition process and permit three-dimensional contour mapping of underside and top portions of the foot in a non-loaded condition, with the possibility of scanning both foot portions simultaneously.
There is thus a need for a novel foot supporting and positioning device capable of maintaining the foot in a desired position in non-loaded conditions while causing negligible interference with contact-free optical measurement apparatus, even when the upper and underside portions of the foot are measured simultaneously, according to a preferred measurement method.
The present invention provides a foot supporting and positioning device and a measurement method advantageously used in co-operation with a contact-free optical three-dimensional measurement system which overcomes the limitations and drawbacks of the above mentioned solutions of the prior art, and more specifically:
a first object of the instant invention is to provide a foot supporting and positioning device which totally or substantially relieves the underside of the foot from the pressure exerted by the weight of the person;
a second object of the present invention is to provide a foot supporting and positioning device which leaves the top and underside portions of the foot free of obstruction for manual or optical acquisition of the three-dimensional measurement information;
a third object of the present invention is to provide a foot supporting and positioning device comprising adjustable means to allow a specialist to position and maintain the foot in a natural or neutral or in any desired position while a measurement process is being carried-out, and without interfering with the process;
a fourth object of the present invention is to provide a foot supporting and positioning device which closely adheres to the foot surface to provide a smooth surface, thus eliminating skin texture and small defects that would have to be corrected on a scanned outer contour image to avoid reproduction of such texture and defects in the insole or last to be fabricated from the acquired dimensional data;
a fifth object of the present invention is to provide a foot supporting and positioning device where the membrane in contact with the foot surface is an inexpensive single-use throw-away stretchable thin membrane;
a sixth object of the present invention is to provide a foot supporting and positioning device providing a separating surface between the upper and underside portions of the foot, thus preventing interference between a upper and a lower measurement apparatus;
a further object of the present invention is to provide a foot measurement method using the foot supporting and positioning device of the present invention and allowing simultaneous optical measurement of the top and underside portions of a foot in a non-loaded condition;
More specifically, in accordance with the invention as broadly claimed, there is provided a foot supporting and positioning device comprising a stretchable envelope made of a thin elastomeric membrane and a support provided with adjustable support members such as hooks, pegs or clips comprising a proximal end and a distal end. The envelope is provided with two lateral wings disposed on opposite sides along the longitudinal axis of said envelope. Said lateral bands are flexible and substantially resistant to axial and lateral elongation and are provided with support member receiving portions such as perforations to receive the distal end of said adjustable members and thereby adjustably supporting and positioning the envelope and the foot inserted therein.
There is also disclosed a measurement method comprising the steps of inserting a foot in a closely fitted thin stretchable envelope provided with support member receiving portions, adjusting the position of said adjustable support members, connecting the sides of the envelope to said members and performing simultaneous or sequential optical measurement of the foot top and underside portions through the stretchable envelope.